Multi-dose hypodermic injector



March 15, 1960 Filed July 15, 1957 3 Sheets-Sheet l l we@ l m f? j Q E /NCL/VTORS.- Q w; ma@ zymmz g ATTORNEYS March 15, 1960 A. vENDlTTY ET AL 2,928,390

MULTI-DOSE HYPODERMIC INJECTOR Filed July 15, 1957 3 Sheets-Sheet 2 /NVENTORS' www@ we 2z By ww/ ATTORNEYS.

March 15, 1960 A. VENDITTY ET AL 2,928,390

MULTI-DOSE HYPODERMIC INJECTOR 3 Sheets-Sheet 3 Filed July 15, 1957 A7' TORNEYS.

United States Patent O MULTI-DOSE HYPODERMIC INJECTOR Anthony Venditty, Detroit, and Lee R. Hammer, St. Clair Shores, Mich., assignors to R. P. Scherer Corporation, a corporation of Michigan Application July 15, 1957, Serial No. 672,022

12 Claims. (Cl. 12S-173) This invention relates to an improved needleless hypodermic injector which is capable of administering one injection after another in rapid sequence. The instrument operates on the same basic principle as the one :shown and described in Robert P. Scherer Patent No. 2,754,818. issued July 17, 1 956. It will discharge medicament from a tiny orifice in a minute stream or jet at two different pressure stages sequentially. The initial lxigh pressure discharge causes the jet stream to distend the skin and force the liquid to a predetermined depth beneath the surface. After the minute opening in the epidermis has been produced, the pressure of the stream is immediately reduced to a lower second stage for completing transfer of the remaining liquid in the dose. The instrument of the present invention dillers from the one shown in Scherer Patent 2,754,818 in that the medicament is not discharged in single doses from individual ampoules, but is dicharged from a chamber within the instrument which chamber is immediately vrefilled after each injection from a container mounted on the instrument.

The primary object of the invention is to provide an improved multiple dose unit which is simple in operation, of sturdy construction and finds particular use in administering mass inoculations, as to members of the armed forces.

Another object is to provide an instrument of this type which is incapable of ejecting fluid medicament until the medicament chamber is lled and disconnected from the source of the medicament, thus insuring performance of operations in proper sequence.

Another object is to provide an instrument constructed in such manner that the parts which come in contact with the medicament comprise a sub-assembly that may be easily removed for sterilization. A further object is toy provide a hydraulically operated instrument employing 'a single flexible conduit for conducting hydraulic fluid both to and from the instrument,

Another object is to provide an instrument which may be simply adjusted to deliver dosages, for example, from 0.2 cc. to l cc.

With these and other objects in view our invention consists in the construction, arrangement and combination of the various parts of our injector whereby the objects contemplated are obtained, as hereinafter more fully set forth, pointed out in our claims and illustrated inthe accompanying drawings, wherein:

"Figure l is a longitudinal section through an instrument constructed in accordance with the invention;

f Figures 2, 3 and 4 are side views of the instrument shown in Figure l, partially broken away to show the position of the various parts as the plunger advances from'retracted to advanced positions;

Figure 5 is a front elevational view of the instrument of Figure 1; -v

Figure 6 is a diagrammatic representation of the powice 2 er means for providing fluid pressure to the instrument and the electrical circuit controlling the power means; Figure 7 is a sectional view taken along theline 7-7 of Figure 1;

Figure 8 is a sectional view taken along the line 8-8 of Figure 1;

Figure 9 is a front elevational view of the spool valve for directing flow of liquid to and from the liquidchamber within the instrument;

Figure l() is a side view of the same valve, rotated from the position shown in Figure 9;

Figures l1 and 12 are side and front views, respectively, of the valve cam which serves to shift the spool valve within the nose of the instrument; and

Figure 13 is an enlarged view of the latch mechanism shown in Figure l with the inclination of the surface 90 being exaggerated.

The hypodermic injector of the invention consists of the instrument proper and-a source of hydraulic power. The body of the instrument 'comprises two cylinders which are telescoped and threaded so that one can be screwed into the other for purposes that will presently become apparent. An injection head comprisingfthe medicament chamber and the ejection orifice is detachably connected to the forward Vcylinder ofthe body. The forward cylinder houses the plunger mechanism which forces the medicamentthrough theorifice. The rear cylinder, which is generally referred to as the spring housing, contains the springs which furnish the motivat-k ing power for operating the unit, and the pistonY which is adapted to compress the springs under the influence of hydraulic fluid introduced into the rearof the spring housing. The springs advance a ram against the plunger in the forward cylinder to force medicament from the medicament chamber under high pressure. A medicament container is mounted on the instrument to supply injection fluid. The power unit consists of a pump for pressurizing hydraulic fluid, such as mineral oil, for use in advancing the piston within the spring housing to compress the springs. v

ln over-all appearance the injector resembles a pistol. It has a trigger which releases a latch that holds the ram against the force of the compressed springs.V The hydraulic fluid line and the control means for actuating the hydraulic fluid mechanism run through the handleof the injector to the power unit.

Injector portiori of instrument The spring housing Vcylinder 13 is of slightly smaller,

diameter than the cylinder 12 and carries threads 18 at the left end, as viewed in-Figure` l, to screw into the threaded end of cylinder 12. Cylinder terminates at the other (forward) end in a cylindrical bore 20 which is adapted to receive a nose member or injection'head 24. The nose member slides into the opening20 Yand has a circumferential flange 21 which abuts against the end 12a of cylinder 12. A blind hole in the right, orrear, end of nose member 24 constitutes an axial cylindrical medicament chamber 25 in which the plunger 22,A is slidably mounted. Medicament chamber 25 terminates' in a small diameter passageway 27 toward the left, or dis' charge end of the nose V24. The outer end o f the nose is of reduced diameter and is externally threaded at 28. A nozzle 24a, which contains a tiny discharge orifice 26,

screws onto the nose and seals against the en d thereofy by means of an O-ring 24h. The medicamentis Vejected #tate ,removal of Athe tube The forward end of bracket -45 terminatesin a clamping tion head sub-assembly., The nut 29 `is externally seriV l rated at29a (FigureS) zto facilitate gripping. It will beV noted ,that the nut 29fhasran inwardly turned flange'SO which is received byfacomplementary step 32 cut in the ange 21 of the nose 24. A valve cam 31, which consists essentiallycf a `ring having an outwardlyv'extending ange 31a (Figure 5)V is mounted rotatablyv-on. 7

the nose 24. Central opening 31e slides Vover` the nose'. It is shownin detail in Figures 1 1 and l2.V An eccentric circular depression cut to aboutfone-half the thickness ofthe ring provides agcircumferential cam surface 38. Flange 31a has a turned edge normal to the plane of the cam ring 31,"Whichv edge is cut to provide a cam surface 52. The purpose of cain surfaces 38 and 52 is disclosed below. The cam also has a" handle 33 xed thereto by means of a screw -34to `facilitate manual manipulation thereof. The valve cam`31 is held in place on the nose by means ofa spool valve 35 which slides into diametrically'extending opening 36 in the nose. The valve cam 31 has a semi-circular depression 31b acrossv the ange side `of the face, the depression being concentric with the 43 for4 sterilization purposes.

tip 45a (Figure 5) which cooperates with serrations 29a on the circumference of collar 29 to lock the collar against rotation.

VThe port 40 extending through the spool valve comes into communie/ation with both the medicament chamber 25 and the minute orifice 26, through passage 27, when the valve cam 31` is rotated in a Vclockwise direction to theon position shown'in broken lines, Figure 5..y AThe designations on and o markedon thevalvefcam indicate the position of ports `3:9, 40. Valve cam '31 has a second cam surface 52 in the edge of Eflange 31a which bears against the endof a nger51-comprising part of switch=53 mounted o-n the 'underside of the cylinder 12 by means of screws 54. As the valve cam 31 is rotated,

ment chamber is in communication with medicament in theY container 44, Vthe hydraulic pressure should' be released topermit the plunger 22fto retractto cause a opening 36. This permits the spool valve to slide into 'f circular openingY 36 when the injection head is being -inif tially assembled. The spool'valve`35ris best V.shown in Figures 9 and 10, and has a pair of rounded surfaces 37h cut intol the ends thereof which are adapted to cooperatewith circular cam surface 4V38 of the valve cam 31.` As indicated, the circular surface 38 is eccentric with respectV to the nose 24 (Figure 5), *which is the centeryabout which the valve cam 31 rotates.v Thus, ,when tbe valve cam is rotated, the spool valve is moved laterally back and forthwith respect-to the passageways 27 and 41. The't betweenthe spool 35 and the opening 36 isvery kclose, say within 25 millionths of an inch, to prevent leakage ofuid. The entire injection head assembly including the nose'24, nozzle 24a, spool valve 35, valve cam 31 and plunger`22 may be removed from the injector `by removing the nut 29. To prevent contamination of the fluid passages by entry of foreign materials between the spool'35 and the opening 36, Orings are'seated in circumferential grooves 37a .on either side of the ports.

The spool valve has two ports 39 and 40. Y In Figure 1 the section Yis taken through port 39 and it will be noted that this port consists of two `interconnect-ing radial passages at right angles to each other.

Port'39 serves to interconnectV the medicamentcharnber 25 with 1a radialv V passage 41 cut intothenose from ythe opening 36. The

other end of the' passage 41A extends. axially and slightly .upwardly so that it emerges 'from the' ange21 to make ,connection with` notch 42 cut;i nto.the upper portion of -the cylinderv l2. The passage 41and notch 42 ,are'adapted ,V

to receive a tube 43 which communicates with ,the con-Y tainer 44 mounted 'on the bracket 45 on Vthe `top of the instrument.` The tube' 43 serves to conduct liquid` medic-V amentrfrom the container 44 to the medicament chamber `25 throughvalve port` 39. Af second tube 46connects.

the interior ofthe container 44 with the atmosphere and mei-lt. :When the screw is `j removed; the;` bracket 45 swings upwardly about the pivot pin 48 as a hinge to facilillirig of the medicament chamber 25 `from thejcontai'uer` 44. On the other hand, when the spool valve is shiftedi Vso that the connection between the medicament chamber 25 and the orifice 26 is complete, the hydraulic pressure` mustthen be actuated to impose a forceV on the piston 1iu the spring housing 13 to compress the Lsprings in prepara'i tion for administering the injection. l This is `accomplished by closing and opening the electrical circuit to a solenoid valve in the hydraulic power-pac as disclosed below. 1 The switch 53 is a standard `microswitch which opens the circuit to the pow-er unit when thelingerl'isde; pressed. Y'1" he spring 55, housed-inthe opening 56 lin rthe wall of cylinder 12, returns the nger 51 -to normal .closed position. Electrical conductors 57, 172 -con nect the switch 53 with 'the power unit which will be described more fully hereinafter. The conductors `emerge i through an opening in the bottom of the handle 16.

The plunger 22 is fittedV closely within themedicament chamber 25 by means `of a molded rubber packing 58 which slides against the chamber wall. Plunger `22 has` a conical nose member 59 and a shaft ltail member 60 which is axially split and `spread* somewhat tomakea frictional connection with plunger holder 61.` A blind opening 62 in the end of the plunger holder 61 urges the spread halves of the inserted shaft together to effect fric-` tional engagement. lnA order `to remove the plunger 22 from the instrument with the injection head assemblyfoxV` sterilization purposes, a stripper ring 63 is rigidly mounted on the right-hand end of the nosemember 24,7Figure 1..A 'The stripper ring has a be-velled lip 64 extending radially inwardly which is of slightlysmallerdiameter than the .1

ange 65 comprising part of the plunger 22. Consequent- 1y, when kthe injectionV head is removed, the stripper lip 64 engages the ange 65 and pulls the plungery free from the plunger holder 61.

Plunger holder 61 terminates at ,the right lend `in a p ,round headf66 which cooperates with force-multiplying means to insure arelatively high injection pressure at the beginning of the plunger stroke. Pressures as-high as 20,000 pounds per square inch are r.desired initially lto penetrate the skin by means of the jet'stream ejected from the orifice 26. Thereafter thev pressure may be reduced to around 3,000 pounds per square inch for the ypurpose cylinder 12 4,to hold thebracket.securelyto jtheainstruplanes inthe form .ofY wedges .67.which bear against the` top surface of the head 66. This construction.isldescribed in detail in the copending applicationgof `(Venditlll:etal.,

Serial No. 442,613, tiled July 12,' 1954, now Patent No.

2,816,543, and forms-no part of the present invention. A wedge plate 68 is slidably disposed within the cylinder 12 and serves to center the plunger holder 61 within the cylinder. The plate contains three radially-extending grooves equally spaced around the circumference, one for each of the wedges 67, to provide ways in .which the wedges slide. A wedge pin 70 is slidably mounted within an opening 71 in the wedge plate 68 and has a forward tubular portion which slides in a bore 74 in the head end of plunger holder 61. A drag ring 77 embraces the tubular portion of the pin 70 and prevents axial movement of the pin except upon application of force. The pin, there.- fore, will not fall out of the 'bore 74. The head of wedge pin 70 has inclined side walls 72 which complement one face of each of the three Wedges 67. As the wedge pin 70 is moved forwardly into the opening 71, the wedges are forced radially outwardly, thus moving the plunger holder 61 and thevattached plunger 22 away from the wedge plate 68. The wedge plate 68 abuts against the end of the'spring housing 13 at 17 and, consequently, the movement must be forwardly.

' A retractor 75, having three legs 76 (as best shown in Figure 8), is adapted to retract the ram member as hereinafter described. The retractor consists of a flat ring 73, having a central opening 7S which encompasses the head of the plunger holder 61; The diameter of opening 78 is considerably larger than the diameter of plunger holder 61. The legs 76 project axially of the injector and bear against the surface of the ram 80. The wedge plate 68 is cut out in three places 68a (Figure 8) to permit legs 76 to pass through. Retraction is accomplished by means of the spring 79 extending between the retractor and the forward end of cylinder 12.

To supply hydraulic fluid to the spring housing 13 a tubular swivel fitting 81 extends through the end plug 84 which screws into the internally threaded opening in the rear end of the housing. The fitting is slip fitted through opening 85 in plug 84 and the space therebetween is sealed with an O-ring 89, lodged in a groove in the wall of opening 85. This construction permits rotation of the housing 13 with respect to the fitting. A retainer ring 86 and a washer 87 hold the fitting against axial displacement. The interior bore 91 through the iitting connects to a tube 92 which in turn is connected to the hydraulic fluid supply tube 94 by angle coupling95.

The plug 84 is sealed where it contacts the housing 13 by means of an O-ring 88. This prevents hydraulic uid within the housing 13 from leaking.

The interior of the housing 13 is divided into six circumferentially-spaced spring wells 99 integrallyformed around a central bore 97, as best shown in Figure 7. Piston member 100, slidably mounted in chamber 93 of housing 13, is adapted to compress the springs 98 which are disposed within wells 99.v Piston 100 has an integral,

forwardly-extending central tube-like member 101 which terminates in an inwardly turned ange 102. A screw 103 extends through the end of the tube-like member 101, its head bearing against the ange 102. The screw is adapted to connect the piston 100 to the ram member 80 as a tension member to prevent the springs from extending beyond their intended limits. The screw 103 may be employed to adjust the precompression of springs 98 by controlling the distance between the end of the ram and the piston 100. The interior of the tube V101 is sealed from hydraulic fluid by means of a plug 104 having an Ofring 105 in contact with the inner surface of the tube 101. The plug is inserted after the screw is assembled with the ram. The piston 100 also has a circumferential groove adapted to receive O-ring 106 which seals the piston against the interior wall of chamber `93. Thus, between the piston 100 and the plug 84 there is a fluid-tight chamber 93 which receives hydraulic uid from the tube 92 for compressing springs 98. t

As indicated, a plurality of springs 98 are spaced cir-l eumferentially within wells .99. Centering pins 107 extend axially forwardv from the. piston lto serve-v 4guides for'the springs.y YThe bore 97 in the center of the housing 13 is adapted to receive the shaft 108 of ram .member 80, which shaft member slides within the b ore 97. The tubular member 101 is disposed within the same opening 97 for axial movement. The ram member80 terminates in a head 109 having a guide pin 110 projecting therefrom for each one of the springs 98. n

The face of the ram head 109 has an inclined edge 111 comprising part of insert 113 which engages a latch member 112 Vto hold the ram against the force of springs 98 when they are compressed. We have found that the surface 111 should preferably be made from a heattreated metal which has good resistance to wear, and for this reason the insert is provided rather than using the ram itself. The latch 112 extends axially of the instrument and has an upwardly turned stud 114 which tits loosely into an opening 115 in the interior of the spring housing 13 to provide hinge action toward and away from the center of the spring housing. The headv of screw 114e holds the stud 114 in the opening 115 to maintain hinge engagement. The latch member 112 has a head 116 with an inclined surface 117 disposed at the same angle as the surface 111 on the insert 113. Thus, when the support for the latch 112 is removed, the force of the springs will cause the latch to slide downwardly out of the way about pivot stud 114 and permit the ram to move forward. Latch support member 118 is pivotally mounted on a pin 119 fixed to a boss extending from the body or forward cylinder 12. The end of latch 112 is adapted to slide along the top upwardly inclined surface 90 of the support member 118 when the housing 13 is advanced with respect to cylinderl 12 as explained below. The inclination of the surface 90 is best shown in Figure 13 where the parts are enlarged and the angle of inclination exaggerated. This design insures the forward force of the ram to be transmitted through the head 116 normal to the surface 90 at any position along that surface. The free end of the support 118 is supported by means of a coil spring 120, one end of which extends into a recess 121 in member 118 and the other end of which seats in a recess 121a in the trigger 122. The trigger is pivotally mounted on pin 123 which extends across the instrument from bosses formed in-y tegrally in the bottom of the body or cylinder 12. It has a stepv 124 in thetop thereof for holding the end of the support 118 while the latch 112 is in operative position.. The spring serves to return the support 118 and the latch 112 to theirl original latched positions. The spring 120 also serves to rotate the trigger back to cocking posi-.Y tion in which position the step 1244supports the latch sup-v port 118 as illustrated in Figure 13.

In order to administer a quantity of medicament less than the full amount carried by the chamber 25, provision is made for rotating the entire spring housing 13 in cylinder 12, including the plunger 22 which is advanced thereby. The threads 18 advance the entire assembly mounted in housing 13 to push the plunger 22 into the chamber 25 a predetermined distance. It will be noted from Figure 3 that there is a scale on the outside surface of handle 16 so that when housing 13 movesy intol the forward cylinder 12, the operator can tell at a glance the position of the plunger inthe chamber. The-marks are calibrated in cubic centimeters so that quantities' of medicament varying from 0.2 cc. to 1 cc. may be administered. The housing 13 must be rotated through a complete revolution if the instrument is'to be operative. This is to make certain that the latch 112, which turns with the housing 13, is always aligned with the stationary latch support 118 after dosage adjustment is coml by depressing the trigger.V

lock sdepressed, and thev latching meelianism'y unlatched A cap127containing an absorbent material saturated with an .antiseptic is adapted to fit over the nozzle of the instrument to keep the end sterile when notin use. 'Y j F luid producing means lThe hydraulic fluid power supply system is best shown in'Figure 6 and is generally referred to as a power-pac.- It consists of asfluid (oil) reservoir 156, a pump 152, an electric motor 154 for driving*V the pump, a solenoid actuated valve 156, a'three-way valve 164 and various conduits "for conducting the pressurized fluid to the instrument when needed and for by-passing the instrument when pressure is not required. The pump is supplied with fluid from the reservoir 159 through discharge line 162 and suction line 166. Return iiowA to the reservoir isthroughnthesupply line S which connects tothe'dis chargeside of the pump 152 throughconduit 160.

A spool valve member-169 withinthree-way valve 164` serves to direct iiow through the by-pass line 168 when oil is flowing fromthe instrument throughline 94, and to close the by-pass line when oil is flowing to the instrument. The valve member is normally spring-biased to open position so that oil may flow from line 94 into bypass line 168. When the solenoid valve, 156 is closed by mature or partial ejection is completelyavoided. `Suitable'mechanical means rather than electrical means may beemployed to actuate valve 156. For example, atiexi` ble push-pull cable connected to the valve cam 31 would ,serve satisfactorily to close and open valve 156 upon illustrated' in'Figure` 1, the instrument is in filled position.

'- "I'he sequence control is eected by means-of the valve cle-energizing the electrical ,circuitconnectingfthereto,

the upstream kpressure in lines 158, 160 builds up, thus closing the valve 169 against .the` force of the biasing spring. The oil discharged from pump 152 then ows to the instrument through hose 94 since this is the only v conduit open. The pumphas an internal relief valve which opens when the pressureinV line 94 builds up to the predetermined maximum required' to operate the instrument.

Motor 154 connectsto a regular 110 volt power supi( 4 Y ply." 'Lead wires 170 and 172 from the Vsame 110 volt sourcesupply power for the solenoid of valve 1756`through the switch 53 on the instrument. The switch makes or breaks the circuit to the solenoid by connecting or disconnecting the electrical path between lines 172 and57.

When the valve cam 31 on the nose of the instrumentis rotated to oit position, the switch 53 is closed, thus actuatingV the solenoid to open valve 156A. Thi'srelieves pressure in lines 160 and 94 which holds valve member 169 closed, and valve 169 opens to permitoil from the instrument to ow Ainto by-pass line 168. Simultaneously, the oil from pump 152 liows through line 160, line 158 and back to the reservoir 150; V V 1 When the Vvalve cam 31 is rotated to` on position cam 31 and the trigger 122; The instrument must irst be primed. by holding the trigger 122 in depressed position and Vrotating the valve catn31 clockwise (Figure 5) t as far as it `willgo to on position and then counterclockwise as far as it will go to the ofi position. This actionV 'alternately iills and empties the chamber ZSto expel air or sterilizing liquid as the case may be. When the valve cam is turned counterclockwise to oli posi'- tion, the instrument is in filled position, as shown in Figure ,1, and the action of the elements is as follows'. V

The spool valve is positioned with port 39 aligned with the chamber 25 so thatvcommunication is established between that chamber 'and the container 44 through tube 43. The valve slides into operative position just before rotation of the cam is complete. Immediately after this connection is made, continued rotation of cam surface 52 closes; thegswitch 53, which actuates the solenoid valve t 156 in the power-pac unit. When the solenoid is actuated, the valve isopcned, which permits tiuid to by-pass the-instrument in themanner previously explained so that there is no pressure being applied to the piston 100. With the fluid resistance gone, the retractng spring 79 is able to forceg'the entireinternal assembly, 'including the ram `and `the springs, as well as the plunger 22, toward the `rear end of the injector. As soon asthe plunger 22 begins to moveto the rear of the chamber 25,' a-vacuum iscreated causingmedicarnent to flow from the container 44 through tube'43 and valve 35 to till the chamber.Y As the springv 79 retracts the movable parts,

the retractor member 75 moves the raml ahead of the ing Y13. Continued movement of the plunger-head 66 Vforces the wedges 67:V out from between the head and the plate 68,V until they occupy theA position shown in Figure l. .The drag ring 77 provides slight resistance to the movement of wedge pin 70 Vto control wedge movement as described above. Spring 125 disposed between the l underside of the head66 and the'retractorg75 .is emthe switch 53 Vis opened, the circuit to the solenoid is Y de-energized and the valve 156 closes. The pressure then begins to build up in line 160 and the valveV member K 169 closes. This causes the oil to flow to the instrument through hose 94. The fluid pressure is usedto compress the springsl in the instrument through the cylinder-piston arrangement previously described. When thet'pres'sure builds up to around 300 pounds persquare inch, which' shown in the drawing.

Itis important, however,l thatV ployed to insure contact between the wedge plate `6B andthe end of the spring housing l80.

As the ram is retracted (without depressing the trigger),

the inclined surface` lll-on thepface thereof movesbe.-

hind. the latch head 116 and the latch snaps up intoposition due to theV forceof the spring k120. `The length of the legs 76 of the retractor 75 issuliicient to insure rc- Y traction of the` ram beyond the headof the latch.` Simul- V.taneou sl.y, the spring 120 `rotates the trigger 122 so thattheshoulder 124 slides `beneath the latch support 118 to hold it in elevated position. Thus, when force is applied to the ram in compressing the spring 98,the ram does` not move forward but remains latched until such timeV `as. the trigger is depressed.

In .order toieject the medicament from the chamber 25 afterv the `instrument has been cocked, `the valve Vcam f 31 is'rotated-in'the clockwise direction yasfar as it will uid. pressure beresponsive to the control of the spool 1 valve 35,50 that pressure is built up only when the. medic-V amant chamber 25. is. filled and theV valve 35 properly aligned with the :dischargev orifice. 27. In this. wayipregoto ,on? position.` This shifts the spool valve 35 laterally so that the port 40 is` Valigned with the opening 27,\

thus making a direct connection between the chamber 25 and the. discharg'e-orice26. At theend of the `stroke` of the valve cam, the switch 53 is opened since the cam surface 52 moves toward the finger 51. lThis closes the solenoid valve 156 and causes the powerpac to build up liuid pressure which is transmitted through the tubes 94 and 92 and passage 91. The oil flows into the chamber 93 and forces the piston 100 forwardly to compress the springs 98. The advance of the piston is arrested when the piston shoulder 130 strikes the shoulder 131 integrally formed with the housing 13 (see Figure 2). At this point the springs are sufficiently compressed to provide the necessary motive force for ejection. The pressure within the chamber 93 is maintained until the valve cam is again turned in the counterclockwise direction (off position) which, of course, occurs after ejection. Consequently, the springs remain compressed until the trigger is depressed. The piston 100 remains immobile during the injection.

When the valve cam 31 is turned back and forth from counterclockwise (oif) to clockwise (on) position several times with the trigger depressed, the action causes the medicament chamber to become filled and emptied until all of the air or other liquid that might have been in the system has been discharged. The liquid is discharged under the force imposed by the hydraulic fluid only since the springs are not compressed while the latch is inoperative.

In administering a hypodermic injection with the instrument, it will be assumed that the chamber 25 is filled and the springs are compressed by means of the hydraulic fluid exerting force against the piston 100, as shown in Figure 2. The nose 24a of the instrument is pressed firmly against the epidermis through which the medicament will be injected. The trigger is then depressed. The ram 80 moves forward very quickly and achieves substantially maximum velocity within the distance between the face of the ram and the top of the wedge pin, indicated in Figure l of the drawing by the-letter X. The impact ofthe ram against the wedge pin forces the wedges 67 outwardly, causing the plunger head 66 and parts connected thereto to move forward. Theplunger holder 61 must necessarily move in the forward direction since the wedge plate 68 is firmly held against retraction by the end 17 of the housing 13. With the forward motion of the plunger holder 61, the plunger 22 is advanced within the chamber 25 to expel medicament atextremely high pressure due to the increased mechanical advantage provided by transmitting the force of the springs through the wedges. As soon as the ram has depressed the wedge pin to the point where the ram picks up the face of vwedge plate 68, the function of the force-multiplying means has been completed and the pressure is reduced to the second, lower stage. The elements are then in the position shown in Figure 3. The ram then advances the entire plunger assembly as a unit and the plunger is advanced to the end of the chamber 25. It will be noted from Figure 4 that the end of the plunger conforms. in shape to the end of the chamber so that the last drop of medicament is expelled therefrom to insure injection of the precise dosage desired.

The instrument must now be refilled and the valve cam 31 is rotated in a counterclockwise direction so that the oil may liow from the chamber 93 back to the power source under the force of the retracting spring 79. All

of the parts are retracted in the sequence described above.

The spool valve 35 is moved laterally so thatthe port 39 connects the chamber 25 with the tube 43. As the plunger 22 retracts, the chamber 2S is again filled with fiuid medicament from container 44.

It may be seen from the foregoing description that the instrument is very easy to operate. Merely by rotating the cam valve back and forth the instrument may be refilled and made ready for another injection. The instrument is designed to administer a maximum o'f 1200 injections per hour.

One ot the important advantages of the injector of the assembly for purposes of sterilization.

and veasily removed.. yThis is accomplished by removing the container44 from the holder 45, removing thegscrew 50 and flipping the holder upwardly about the hinge pin 58. This avoids interference by the holder with removal of the tubes 43 and 46. The collarv nut 29 is then unscrewed. This permits pulling the nose 24, including the tube 43 and the plunger 22, from the cylinder 12. The stripper ring 63 insures removal of the plunger 22 with the nose since the lip 64 thereof bears against the ange 65 of the plunger. The shaft 60 of the plunger pulls out of the opening 62 in the plunger holder 61 since it is connected only by a friction-fit. The removed parts are then sterilized as a unit and reassembled on the instru- Iment. This procedure is seldom necessary, however.

Y again the antiseptic is washed out with sterile water by running through, say, ten cycles with the trigger depressed. The container 44 holding the medicament to be injected is lthen placed in the holder and the instrument is primed as described above by firing two or three times to remove all the water from the chamber 25 and conduits connecting thereto. j

Other modifications of the invention Will .ocur to those skilled in the art. In is not our intention to limit the invention to theV specific forms illustrated herein other than as necessitated by the scope of the appended claims.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A multiple dose hypodermic injector-comprising a cylinder terminating in a nose containing an ejection orifice, a medicament chamber within said cylinder, a plunger disposed within said chamber, spring means for advancing said plunger to eject medicament through said orifice,` a piston slidably mounted in said cylinder, Huid pressure means responsive to control means mounted on said cylinder for forcing fluid into said cylinder against said piston to compress said springs, a movable valve mounted in said nose for connecting said chamber with a source of medicament in a first position and for connecting said chamber with said orifice in a second position, and cam means mounted on said cylinder for actu- 1 ating said control means and said movable valve simultaneously to cut off fluid pressure to said cylinder when Vsaid valve is in s aid first position and to build up uid Y chamber and plunger are removable from said cylinder for sterilization.

3. The injector of claim 1 wherein said uid pressure means is separatev from the injector and constitutes a liquid reservoir, a lpump for pressurizing said liquid and a single flexible tube connecting said pump to` said cylinder for fluid ow therethrough.

4. The injector of claim 1 lwherein force multiplying means is disposed between said spring means and said plunger to increase the force on the plunger during the initial portion of its ejection stroke.

5. A multiple dose hypodermic injector comprising a cylinder terminating in a nose containing an ejection orifice, a medicament chamber within said cylinder, a plunger disposed within said chamber, spring means for advancing said plunger to eject medicament through said orifice, a piston slidably mounted in said cylinder, fiud pressure means connecting with said cylinder responsive to control means for forcing fluid into said cylinder against said piston to compress said spring means, a valve mounted in said nose having a first and a second port, said first port serving to connect said chamber with a source of medicament and said second port serving ftd connect said V"chamber "with said orifrceff'said control jfmean's beingmounted on 'said Acylinder adjacent said nose, a valve 'camrotatably mounted lcinrsaid nose adapted Vvto 'rotate-in-'one direction to shiftjsid valve to-place said first port in qperativepositionvand cause said 'Acontrol meansY to cut oi tiuid pressure'rto the cylinder when Asaid lirst port is in communicationfjwit'h said chamber;

aanstaan ndei'- and 'having a Yhead adapted to engage the face of i saidgramto hold` theram against the compressive force j of saidA springs, .aV latch support t member pivotally mounted onsaid body beneathsaidV latch and axially aligned therewith, said support member `having anV axial- 'l'yV inclined bearing surface which progressively lifts and adapted to rotate in .the` other direction to shift said n valve toV place said second port in operative position and cauvse'said control means to build upriluidA pressure in said cylinder when saidsecondY port'isiinrcommunication with `said chamber. y l Y.

'6, The injector lof `claim 5 wherein said `lluidpressure neans constitutes a li'quidreservoir, a pumpn for pressurizing vsaid-liquid drawn from. said reservoir, a tube connecting said pump, to. said.. cylinder, a returnv from "d 'said p umpfto said reservoir and a solenoid actuatedrvalve Vwith said chamber when `said latch as'the housing is advanced with respect to V phere to vent the container.

insaid returnline Yand wherein said ,control means confstitutes'a switch for interrupting powerfflow torsaid solenoid.

f7. A .rnultiple Ydose hypodermic` injector comprising` va body having a forward'cylind'er terminating'in a nose Y containing anejection o'rice, a liquidV medicament chamrber` within' said cylinder fin communication YLwithls'aid i oriiic`e,a spool valve Vmounted for axialvino'vement within `said-nose foi-'connecting said chamber withY a sourceV of medicament ina first position andpfor connecting said chamber with said orifice in a secondjpositin, anda plunger disposed within/said` chamber, saidA body also having a rearward cylindricalspring 'housing ,connected to said `forward cylinder, said housing ,containing a ram for advancing said plunger within saidcha'niber, a plurality of springs for driving said ram, 'a `piston disposed within said housing rearwardly of said springs.lluidV pressure means forforcing `tiuid into the rear of said housing to move saidpiston forwardly and compress said springs, control means mounted on saidjforward cylinder for actuating said uid pressure means, and a camk member rotatably mountedV on said nose Vfoi' actuating simultaneously said control means andv said spool v alve to cut of lipid pressureto said housing when said valve isin said r'st position and to build up iuid pressure in lsaid: housing when said valve is in saidfsecond position.

8. The injector of claim 7 including a latch mounted on 'said housing for holdingrsaid ram against the coinpressive force Y,of said springs.

9. vThe injector of claim 7 includinga handle secured to said body, latch pivotally mounted Von said housing for radial movement with respect to said cyl- 12K. `A multiple dose hypoderinic injector comprising V"afcylinderterminating in a noseco'ntainfng an ejection V orifice, a medicament chamber within Vsaid cylinder in communication with said orice, a plunger disposed within said vchamberfor ejecting medicament through said'oriiice a plunger holder connected to saidiplunger andgterminating at its rearwardvend in a head, a ram slidably disposed in said cylinder for advancing said plunger with in said `chambenspring means for driving 'said ram, fluid pressure'rneansincluding a piston for compressingxsaid springs, force-multiplying means disyposed between said head and said ram for increasing the force on said plunger during the initial portion of the plunger stroke, a retractorA spring disposed between the forward end of said cylinderand said head forfretracting said plunger, said Aforce-multiplying means and said rain;

and a ring-'like rain Vreti-actor,encircling saidplunger 'holder between said retractor spring and said head and having a plurality of axially-disposed legs which extend rearwardly'b'eyond said force-multiplying means and bear against the face of said ram to vmaintain said ram in t spaced Vrelation withsaid force-multiplyin'gmeans dui"-` ing retraction.

ReferencesCited in the tile of this patent UNITED STATES PATENTS V2,821,193 ziiieri Jan. r2s, 195s Y i FOREIGNPATENTSv d, 732,508Y fGreatBritain ---.i June 22,'1955 -766,431 d Great Britain .4. J an. '23, 1957 

